The relationship of endogenous depression to abnormalities in the hypothalamic/pituitary/adrenal axis is explored in the serach for endocrine markers of the disorder. Brain and pituitary peptidergic systems (corticotropin (ACTH), beta-endorphin, their common precursor molecule, melanocyte stimulating hormone, and related peptides) are studied in depressed patients and normal control subjects. The link between the dexamethasone suppression test and ACTH levels is explored.